In recent years, environmental issues such as global warming and the like that are attributed to increases in carbon dioxide have become serious. As a result, non-silicon solar cells have gained attention as solar cells that have little environmental impact and that also allow for reduced manufacturing costs; and research and development of such is moving forward.
Among non-silicon solar cells, the dye-sensitized solar cell developed by Graetzel et al. in Switzerland has attracted attention as a new type of solar cell. As a solar cell using organic materials, these solar cells have advantages such as high photoelectric conversion efficiency and lower manufacturing costs than silicon solar cells.
However, dye-sensitized solar cells are electrochemical cells, and therefore use organic electrolytic solutions and/or ionic liquids as electrolytes. In cases where organic electrolytic solutions are used, there is a problem in that electrical efficiency decreases due to volitization and depletion during long-term use. Additionally, in cases where ionic liquids are used, while volitization and depletion that occur during long-term use can be prevented, there are durability problems such as structural degradation caused by liquid leakage.
Therefore, research is being conducted regarding converting the electrolyte from a liquid to a gel or solid for the purpose of preventing the volitization and liquid leakage of the electrolytic solution and ensuring the long-term stability and durability of the solar cell.
For example, Patent Document 1 describes an electrolyte composition including an ionic liquid and conductive particles as main components, wherein the electrolyte composition is made into a gel (Claims 1 and 2).
Additionally, Patent Document 2 describes a dye-sensitized photoelectric conversion element having a porous photoelectrode layer made from dye-sensitized semiconductor particles, a charge transport layer, and a counterelectrode layer in this order. The charge transport layer is made from a solid mixture including from 1 to 50 mass % of a p-type conductive polymer, from 5 to 50 mass % of a carbon material, and from 20 to 85 mass % of an ionic liquid (Claim 1).
However, in cases where the electrolyte composition described in Patent Document 1 is used, when a redox couple (particularly iodine) is used in order to achieve high energy conversion efficiency, there have been problems such as the metal wiring (collecting electrode), seal material, and the like that constitute the photoelectric conversion element being corroded due to the corrosive properties of the iodine; and the stability of the electrolyte being affected due to the volatility of the iodine.